1. Field of the Invention
The invention relates to a powder coating composition comprising (a) a resin, (b) a curing agent and (c) zinc.
2. Description of the Prior Art
Such compositions are generally well-known in the art. See, for example, U.S. Pat. No. 4,381,334 and DE-A-3,018,765, both of which are incorporated by reference herein for all purposes.
In U.S. Pat. No. 4,381,334, 75-90% by weight of zinc dust are extruded with a thermosetting binder (an epoxy resin) and, optionally, a curing agent therefor. In DE-A-3,018,765, 60-90% by weight zinc dust are extruded with the thermosetting binder and at least an extra 2-25% by weight zinc dust are then admixed to the ground extrudate. These powder coatings are applied as corrosion protective films.
A disadvantage of these compositions is the appearance of segregation between the resin and zinc dust as indicated by DE-A-3,018,765.